Hybrid energy systems typically include a an engine having its prime mover, e.g., a crankshaft, mechanically decoupled from a driven load, e.g., a transmission operatively connected to one or more traction devices. The engine is usually hydraulically or electrically coupled to the load allowing the engine to operate as an energy source rather than a conventional drive mechanism. As such, the engine may be operable at a relatively more desirable operating condition, e.g., at an operating condition consuming relatively less fuel. However, engine output at a given operating condition may be insufficient to satisfy demanded energy, e.g., when an operator and/or the driven load demands more energy than the engine is capable of outputting at the given operating condition. Hybrid energy systems usually also include an energy storage device to receive energy from the engine when engine output is sufficient to satisfy the demanded energy and provide additional energy to the driven load when engine output is insufficient. Controlling the operating condition of the engine, the amount and/or timing of energy delivered from the engine to the energy storage device, and the amount of energy available from the energy storage device, may impact the benefits achievable by a hybrid energy system with respect to conventional drive mechanisms.
U.S. Pat. No. 7,137,344 (“the '344 patent”) issued to Kumar et al. discloses a hybrid energy load control system and two control methods. Each method includes sensing the current power generated by a power source and sensing a commanded power of the power source by monitoring an operator input. Each method also determines the difference between the current power and the commanded power and controls the delivery of power from the power source to a driven load and to an energy storage system. In the first method, if the current power is less than the commanded power, a controller increases the power output to exceed the commanded power and directs the portion of the increased power that exceeds the commanded power to the energy storage system. In the first method, if the current power is greater than the commanded power, the controller maintains the current power and directs the portion of the current power that exceeds the commanded power to the energy storage system. In the second method, if the current power is less than the commanded power, the controller increases the power output and directs power within the energy storage system to the driven load. In each method, the controller ceases to direct a portion of the power output to the energy storage system after an elapsed period of time.
Although, the methods of the '344 patent may control the delivery of power from the power source to the driven load and the energy storage system as a function of the difference between the current and commanded power, the power source may direct power to the energy storage device during high load scenarios. Additionally, by not monitoring the power within the energy storage device, the methods of the '344 patent may passively direct energy thereto instead of optimizing the amount of energy directed to and stored within the energy storage device. Each of which may increase the frequency of the power source operating in relatively less desirable operating condition, e.g., an operating condition having relatively high fuel consumption or relatively high emissions.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above.